My one gerbil died last night (aged 3) from cancer . This has left his brother (also 3) lonely. He's franticly looking for him and keeps digging in the spot he died . I don't want to introduce one gerbil as I don't want the same problem when my old one goes but I'm not keen on introducing more gerbils as I don't want to stress my old one out . I'm not sure what to do as he is stressed and it breaks my heart to see him like this.